Ich war gestern zu Hause.
English: I was at home yesterday.
The Präteritum is the simple past tense in German. 'Sein' (to be) and 'haben' (to have) have special forms in the Präteritum. These forms are used to talk about things that happened in the past.
In German, the Präteritum forms of 'sein' and 'haben' are often used in written texts, stories, and reports to describe past events or situations. In spoken German, they are also common for these two verbs.
Ich war gestern zu Hause.
English: I was at home yesterday.
Wir hatten keine Zeit.
English: We had no time.
Er war sehr müde.
English: He was very tired.
Sie hatten Glück.
English: They were lucky.